add: canonical linkを追加

src/routes/(DefaultStyle)/[slug]/+page.svelte

@@ -1,8 +1,15 @@
 <script>
 	const { data } = $props();
 	import Postgrid from './grid.svelte'
+
+	import { base } from '$app/paths';
+	import { PUBLIC_HOSTNAME } from '$env/static/public';
 </script>
 
+<svelte:head>
+	<link rel="canonical" href="https://{PUBLIC_HOSTNAME}{base}/" />
+</svelte:head>
+
 
 <div class='contain'>
 	<div class="posts">